The aim of this project is to understand the mechanism by which the rat liver organelle, the peroxisome, is formed. The organelle is involved in the metabolism of hydrogen peroxide and the oxidation of ethanol, and is implicated in lipid metabolism. Isotopic labeling, cell fractionation, biochemical analyses, and immunochemical precipitations will be employed. Peroxisomes will be purified and fractionated into their insoluble cores and 3 classes of soluble proteins. Antibodies against each of the protein fractions wlll be prepared, characterized and purified. H3-leucine will be injected into rats, which will be sacrificed 3-60 minutes later. A postnuclear fraction prepared from the liver will be subfractionated on a continuous sucrose gradient. The fractions will be analyzed enzymatically to locate the marker enzymes and thus the organelles. Each of the classes of peroxisomal proteins will be purified immunochemically from each gradient fraction, and its radioactivity determined, in order to locate the newly made proteins. The route that each class of proteins takes through the cell will be compared with that of catalase, which has been determined previously (Lazarow and de Duve, 1973) in order to find out whether different peroxisomal proteins follow the same route. Other experiments will be performed to determine the site of synthesis of catalase, and whether it passes through the cell sap or a fragile structure immediately after it is made. When the basic features of the intracellular transport of peroxisomal proteins are clear, various drugs known to affect peroxisome formation will be examined for their effect on the transport process, in the hopes of elucidating the mechanisms regulating transport.